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8/18/2019 Study of Distributed Coordination Function (Dcf) and Enhanced Dcf (Edcf) in 802.11 Mac Protocols for Multimedia (…
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Study of Distributed Coordination Function (DCF) and Enhanced DCF
(EDCF) in IEEE 802.11 MAC Protocols for Multimedia Applications
Chan Chen Hoong
Bachelor of Engineering with Honors
(Electronics & Computer Engineering)
2009/2010
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STUDY OF DISTRIBUTED COORDINATION FUNCTION (DCF) AND
ENHANCED DCF (EDCF) IN 802.11 MAC PROTOCOLS FOR MULTIMEDIA
APPLICATIONS.
CHAN CHEN HOONG
This project is submitted in partial fulfillment of
The requirements for the degree of Bachelor of Engineering with Honors(Electronic and Computer Engineering)
Faculty of Engineering
UNIVERSITI MALAYSIA SARAWAK
2010
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Dedicated to my beloved family and friends
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UNIVERSITI MALAYSIA SARAWAK
R13a
BORANG PENGESAHAN STATUS TESIS
Judul: STUDY OF DISTRIBUTED COORDINATION FUNCTION (DCF)
AND ENHANCED DCF (EDCF) IN 802.11 MAC PROTOCOLS FOR
MULTIMEDIA APPLICATIONS
SESI PENGAJIAN: 2006 – 2010
Saya CHAN CHEN HOONG
(HURUF BESAR)
mengaku membenarkan tesis * ini disimpan di Pusat Khidmat Maklumat Akademik, Universiti Malaysia
Sarawak dengan syarat-syarat kegunaan seperti berikut:
1. Tesis adalah hakmilik Universiti Malaysia Sarawak.2. Pusat Khidmat Maklumat Akademik, Universiti Malaysia Sarawak dibenarkan membuat salinan untuk
tujuan pengajian sahaja.
3. Membuat pendigitan untuk membangunkan Pangkalan Data Kandungan Tempatan.4. Pusat Khidmat Maklumat Akademik, Universiti Malaysia Sarawak dibenarkan membuat salinan tesis
ini sebagai bahan pertukaran antara institusi pengajian tinggi.5. ** Sila tandakan ( ) di kotak yang berkenaan
SULIT (Mengandungi maklumat yang berdarjah keselamatan atau kepentingan
Malaysia seperti yang termaktub di dalam AKTA RAHSIA RASMI 1972).
TERHAD (Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/
badan di mana penyelidikan dijalankan).
TIDAK TERHAD
Disahkan oleh
(TANDATANGAN PENULIS) (TANDATANGAN PENYELIA)
Alamat tetap: 81, JALAN 20/946300, PETALING JAYA
SELANGOR DARUL EHSAN DR HUSHAIRI ZEN
(Nama Penyelia)
Tarikh: 24 March 2010 Tarikh:
CATATAN * Tesis dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah, Sarjana dan Sarjana Muda.
** Jika tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai
SULIT dan TERHAD.
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The Following Final Year Project:
Title : Study of Distributed Coordination Function (DCF) and Enhanced
DCF (EDCF) in 802.11 MAC Protocols for Multimedia
Applications.
Author : Chan Chen Hoong
Matric number : 16056
has been read and certified by:
_______________________________ ______________
Dr Hushairi Zen Date
(Supervisor)
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ii
ACKNOWLEDGEMENT
This project was made possible as a result of the co-operation and support given
by several parties. Though I am not able to list down all of them, rest assured I am
grateful for their assistance no matter how or what their contribution may be.
A very special note of appreciation is extended to my supportive Final Year
Project supervisor, Dr Hushairi Zen for to his undying patience, enlightening advices,
constructive comments and constant guidance throughout the course of the project. Also,
I would like to dedicate a special gratitude to Pn. Ade Syaheda Wani (as the Final Year
Project Coordinator) and to Yu Ka Chai, Lee Liang Wee and Punitha Subbramaniam for
being excellent colleagues in our clique of NS-2 networking projects.
Last but definitely not least, I would like to thank my family and friends for all
their love, care, support and companion that had helped me in surviving times of
insurmountable odds and making my educational years a wonderful and hopefully a
successful one.
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ABSTRAK
IEEE 802.11e Kawalan Kemasukan Medium ( MAC ) merupakan satu penambah-baikan
kepada piawaian IEEE 802.11 rangkaian kawasan tempatan tanpa wayar (WLAN ) untuk
menyokong kualiti servis (QoS). 802.11e MAC adalah berdasarkan kepada kawalan
berpusat dan juga capaian medium secara bertanding. Projek ini meliputi penilaian
mekanisma capaian medium secara bertanding yang diperbaiki iaitu Fungsi
Penyelarasan Pengedaran yang Ditingkatkan ( EDCF ), berbanding dengan 802.11 MAC ,
Fungsi Penyelarasan Pengedaran ( DCF ) yang asal. Tiga jenis trafik multimedia
dipertimbangkan dalam projek ini adalah suara, video dan data. Penilaian tersebut
dilaksanakan menggunakan simulasi NS-2 (versi 2.34) di dalam Ubuntu, sebuah sistem
operasi Linux. Metrik-metrik yang digunakan dalam penafsiran ini adalah jumlah hasil
proses, masa tangguh, ketaran dan jumlah kehilangan paket. Berdasarkan pada graf bagi
keempat-empat metrik ini, prestasi EDCF dan DCF telah ditafsirkan. Selain itu, had
kemampuan EDCF dapat dikenalpasti melalui simulasi menggunakan bilangan aliran
trafik yang dimanipulasikan. Melalui kajian simulasi ini, kesimpulan yang didapati ialah
EDCF boleh menyediakan capaian medium yang berbeza untuk setiap jenis trafik. Hasil
simulasi menunjukkan prestasi EDCF adalah lebih baik berbanding dengan DCF .
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ABSTRACT
IEEE 802.11e Medium Access Control (MAC) is an enhancement to the legacy IEEE
802.11 standard’s Wireless Local Area Network (WLAN) ideally to support Quality-of-
Service (QOS). The 802.11e MAC is both centrally-controlled and contention-based
channel accesses based. This project covers evaluation of the contention-based channel
access mechanism, called Enhanced Distributed Coordination Function (EDCF), in
comparison with the 802.11 legacy MAC, Distributed Coordination Function. Three
different types of multimedia traffic are considered namely, voice, video and data. The
evaluation was performed using ns-2 simulator (version 2.34) on Linux Ubuntu. The
metrics used in the evaluation are throughput, delay, jitters and packet loss. The graphs
from the metrics benchmarked the performance of EDCF and DCF evaluation. Through
this simulation study, EDCF conclusively provides differentiated channel access for
various multimedia traffic types. Simulation results proved that comparatively EDCF
performs better performance than legacy DCF.
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TABLE OF CONTENTS
CONTENT PAGES
ACKNOWLEDGEMENT ii
ABSTRAK iii
ABSTRACT iv
LIST OF TABLES xi
LIST OF FIGURES xii
LIST OF ABBREVIATIONS xvi
CHAPTER 1 INTRODUCTION
1.1 Introduction 1
1.2 Problem Statement 3
1.3 Project Objective 4
1.4 Scope of Project 4
1.5 Project Outlines 5
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CHAPTER 2 LITERATURE REVIEW
2.1 Project Background 7
2.2 802.11 DCF 11
2.3 802.11e EDCF 18
2.4 Related Works 23
2.5 Network Simulator 2 27
2.6 ITU-T Recommendations 30
CHAPTER 3 METHODOLOGY
3.1 Introduction 32
3.2 Patching EDCF into NS-2.34 34
3.3 Simulation Cases 37
3.3.1 Case 1 - Topology used to compare performances of DCF 38
and EDCF
3.3.2 Case 2 – Topology to Study the Limitation of Multimedia 40
Stream using EDCF
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3.5 Simulation Parameter Values 43
3.6 Analyses Metrics 44
3.6.1 Throughput 45
3.6.2 Delay 46
3.6.3 Packet Loss 47
3.6.4 Jitter 48
CHAPTER 4 RESULTS AND DISCUSSIONS
4.1 Introduction 49
4.2 Performance Study of DCF versus EDCF 49
4.2.1 Trace Files for DCF and EDCF 50
4.2.2 Comparison for DCF and EDCF 51
4.3 Determining the Limitation of Number of Nodes under EDCF 56
4.3.1 Trace Files for Individual Multimedia Traffics 57
4.3.2 Discussions for Simulations of Multimedia Traffics 60
4.3.3 NAM File for Multimedia Traffic 66
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4.4 Problems Encountered and Troubleshooting 69
CHAPTER 5 CONCLUSION AND FUTURE WORK
5.1 Conclusion 70
5.2 Recommendations 71
REFERENCES 72
APPENDICES
APPENDIX A 76
APPENDIX B 83
APPENDIX C 90
APPENDIX D 99
APPENDIX E 102
APPENDIX F 105
APPENDIX G 108
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LIST OF TABLES
TABLES PAGES
2.1 Different Interframe Spacing 14
2.2 Parameters used in Legacy 802.11b PHY 17
2.3 Priority to Access Category Mappings 19
2.4 Default EDCF Parameters for Simulations 22
2.5 Multimedia Traffic Types and their Characteristics 24
3.1 Multimedia Types and their Characteristics 38
3.2 EDCF Simulation Parameters 43
3.3 Legacy 802.11b Simulation Parameters 44
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x
LIST OF FIGURES
FIGURES PAGES
2.1 MAC and PHY layer 9
2.2 Access Mechanism in MAC Layer 10
2.3 Flow chart of the process of sending data packets under the 12
CSMA/CA based Distributed Coordination Function (DCF).
2.4 DCF CSMA/CA 12
2.5 Legacy IEEE 802.11 DCF Channel Access 15
2.6 IEEE 802.11e EDCF Channel Access 20
2.7 Four access categories (ACs) for EDCF 21
2.8 Comparison of Throughput (bits/sec) Between 25
DCF and EDCF for Various Multimedia Type
2.9 Comparison of Data Dropped (bps) Between 25
DCF and EDCF for Various Multimedia Type
2.10 Comparison of Delay (sec) Between 26
DCF and EDCF for Various Multimedia Type
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3.1 Project Flow Chart 33
3.2 Simulation Case 1 39
3.3 Simulation Case 2 For Voice and Video Traffic 41
3.4 Simulation Case 2 For Data Traffic 42
3.5 End to End Delay 46
4.1 DCF Trace File (EDCF trace file exhibits similar 50
characteristics as its DCF counter part)
4.2 Delay with DCF 52
4.3 Delay with EDCF 53
4.4 Packet Loss with DCF 53
4.5 Packet Loss with EDCF 54
4.6 Throughput with DCF 54
4.7 Throughput with EDCF 55
4.8 Jitters with DCF 55
4.9 Jitters with EDCF 56
4.10 Trace File for Voice Traffic 57
4.11 Trace File for Video Traffic 58
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4.12 Trace File for Data Traffic 59
4.13 Voice Delay for Different Number of Nodes 61
4.14 Voice Packet Loss for Different Number of Nodes 62
4.15 Voice Throughput for Different Number of Nodes 62
4.16 Voice Jitter for Different Number of Nodes 63
4.17 Video Delay for Different Number of Nodes 63
4.18 Video Packet Loss for Different Number of Nodes 64
4.19 Video Throughput for Different Number of Nodes 64
4.20 Video Jitter for Different Number of Nodes 65
4.21 Data Packet Loss for Different Number of Nodes 65
4.22 Data Throughput for Different Number of Nodes 66
4.23 NAM Visualization for Voice Traffic 72
4.24 NAM Visualization for Video Traffic 73
4.25 NAM Visualization for Data Traffic 73
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LIST OF ABBREVIATION
ACK - Acknowledge
AIFS - Arbitration Interframe Spacing
AP - Access Point
BSS - Base Service Set
CBR - Constant Bit Rate
CFB - Contention Free Burst
CSMA - Carrier Sense Multiple Access
CTS - Clear To Send
CWn - Contention Window
DCF - Distributed Coordination Function
DDRR - Distributed Deficit Round Robin
DFS - Distributed Fair Scheduling
DIDD - Double Increment Double Decrement
DIFS - DCF Interframe Spacing
DWFQ - Distributed Weighted Fair Queuing
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xiv
EDCF - Enhanced Distributed Coordination Function
EIFS - Extended Interframe Spacing
FTP - File Transfer Protocol
HTTP - Hypertext Transfer Protocol
IEEE - Institute of Electrical & Electronics Engineers
IFS - Interframe Spacing
IP - Internet Protocol
ITU-T - ITU Telecommunication Standardization Sector
LAN - Local Area Network
LLC - Logical Link Control
MAC - Media Access Control
MSDU - MAC Service Data Unit
Nx - Node
NAV - Network Allocation Vector
NS-2 - Network Simulator 2
PCF - Point Coordination Function
PHY - Physical
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PIFS - PCF Interframe Spacing
QoS - Quality of Service
RTS - Request To Send
SIFS - Short Interframe Spacing
STA - Station
TCL - Tool Command Language
TCP - Transmission Control Protocol
TXOP - Transmission Opportunity
TCP/IP - TCP for Transport Control Protocol/Internet Protocol
UDP - User Datagram Protocol
WLAN - Wireless Local Area Network
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CHAPTER 1
INTRODUCTION
1.1 Introduction
The IEEE 802.11 wireless local area network (WLAN) technology has been a
worldwide preference in terms of affordability, simplicity and flexibility convenience.
This leading deployed wireless technology provides a network environment that is
ubiquitously found in various locations such as café, offices, airport and universities for
conventional data applications along with multimedia applications sharing. This high
demand by public is concurrent with the significant growth in multimedia application
usage such as teleconferencing, media transfer, streaming videos and online gaming.
The IEEE 802.11 Working Groups had employed various task groups that are
actively developing improved revisions of the standard [1][2]. This standard comprises of
the Physical Layer (PHY) and Medium Access Control (MAC) specifications for WLAN
[3]. Improvements include allocation of higher data rates to be used under the PHY
specifications.
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2
However, high data rate alone does not guarantee support of Quality of Service
(QoS) requirements needed in applications such as real time voice, video and audio. The
lack of real time QoS support in WLAN has led to studies of Distributed Coordination
Function (DCF) mode of 802.11 MAC using data application models on an ad hoc
simulator [4]; the architecture and scheduling problems in supporting real time traffic are
addressed based on the optional Point Coordination Function (PCF) mode of 802.11
MAC [5] [6]; service differentiation issues based on DCF are investigated in [7] and [8]
by varying the MAC parameters for different traffic.
The ad-hoc simulator’s architecture is basically similar to the IEEE 802.11e task
group in defining the new Enhanced Distributed Coordination Function (EDCF) [9] MAC
access method as a standard for QoS enhancement of 802.11 MAC.
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1.2 Problem Statement
The legacy 802.11 is governed by two access methods; the Distributed
Coordination Function (DCF) and Point Coordination Function (PCF). With QoS support
being the center of interest, DCF in legacy 802.11 is noted for being unable to support the
concept of differentiating frames with different priorities. Ideally, the DCF is expected to
provide a channel access with equal probabilities to all stations contending for the
channel access in a circulated manner. That being said, equal access probabilities are not
desirable among stations with different priority frames. The emerging Enhanced DCF
(EDCF) is designed to provide differentiated, distributed channel accesses for frames
with different priorities. As proposed, EDCF provides better performance enhancement
for real time traffic as compared to DCF. Thus, a study is required to analyze to what
extent EDCF is better over DCF and what are the limitations of EDCF for various
multimedia traffic scenarios under ITU-T requirements [10].
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1.3 Project Objective
The objective of this project is as followed
i. To understand and learn to use Network Simulator (NS-2) Software
ii. To evaluate and compare the network performance of Enhanced
Distributed Coordination Function (EDCF) versus legacy Distributed
Coordination Function (DCF) access mechanisms in IEEE 802.11
Wireless LANS by means of a comprehensive set of well known traffic
patterns (voice, video and data) and NS-2 as a simulation tool [11].
iii. To provide quantitative results on how the 802.11e standard makes a
difference in QoS architecture governed WLAN.
iv.
To determine the limitation of nodes for individual traffic type that can
fulfill ITU-T requirements for EDCF.
1.4 Scope of Project
This project focuses on DCF and EDCF access mechanism that are the basic of
802.11 and 802.11e MAC access protocol respectively. By using both DCF and EDCF,
the evaluation of each traffic type is carried out individually with different number of
traffic nodes.
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1.5 Project Outlines
The Final Year Project Report records the project’s overall progress from the
preliminary idea development till the project execution and analysis. It is essentially
divided into five chapters, which are introduction; literature review; methodology; results,
analysis and discussion and, conclusion and recommendations. The brief information of
each chapter is described below:
Chapter 1 reviews the aims and purpose of the project as to its relevance,
practicality and appeal. The introduction also assesses the description of the approach to
the problem and its context. It also explains the brief outline of the structure of the
following chapters.
Chapter 2 summarizes and reviews the overall studies and researches which are
related to the project. The literature review covered several researches regarding MAC
protocol, the mechanisms of DCF & EDCF, NS-2 and ITU-T standards.
Chapter 3 discusses the methodology development as well as the NS-2 simulation
tool that is thoroughly used in this project.